Apache Flink is an open-source stream processing framework designed for real-time data processing. It allows developers to build applications that can process large volumes of data continuously and in a fault-tolerant manner. Flink supports both batch and stream processing, making it versatile for various data processing needs. One of the key features of Apache Flink is its ability to handle event time processing, which means it can manage data that arrives out of order. This capability is essential for applications in fields like finance and telecommunications, where timely and accurate data analysis is crucial for decision-making.